The present invention relates generally to systems for reproducing information stored on storage media such as optical discs and more particularly to an integrated apparatus and method for facilitating the reproduction of information read from optical storage discs of different types such as digital video discs (DVDs) and compact discs (CDs).
The transition of audio and video storage from the analog domain to the digital domain has revolutionized the way in which audio and video information is distributed to consumers. For example, digital optical storage media such as CDs and DVDs are quickly becoming the media of choice for distribution of information. The rising popularity of optical storage media, such as CDs and DVDs, has given rise to an expanding market for playback systems which are capable of reproducing information recorded on optical storage discs. Further, since the optical discs may store information encoded in different formats, playback systems which are capable of reading and reproducing information stored in various formats are preferred. Examples of such integrated playback systems include DVD/CD players which are capable of reading and reproducing information stored on CDs and DVDs.
FIG. 1 depicts a typical prior art playback system 1 used for reproducing information stored on CDs and DVDs. Traditional playback system 1 typically includes a disc motor 6 for rotating disc 2, an optical pickup (OPU) subsystem 4, a current-voltage (I/V) amplifier 8, a signal amplifier 10, a servo error detector 12, servo control subsystem 14, servo drivers 16, a read channel (RC) 18, a CD digital signal processor (CD-DSP) 22 along with its associated memory 24, a digital audio processor 34, a DVD DSP 26 along with its associated memory 28, a block decoder 30 along with its associated memory 32, an Advanced Technology Attachment Packet Interface (ATAPI) interface 36, a host system central processing unit (CPU) 38, a MPEG decoder 40 (MPEG-1 or MPEG-2) along with its associated memory 42, audio playback subsystem 44, video playback subsystem 46, a microcontroller 48 coupled with CD/DVD subsystems, and a microcontroller 49 coupled with MPEG decoder 40.
Disc motor 6 typically includes a spindle motor which rotates disc 2 to a desired speed. Servo drivers 16 output currents to disc motor 6 to drive and control the rate of rotations of motors contained in disc motor 6. Servo drivers 16 also output currents to OPU 4 to position OPU 4 on the desired location of disc 2, to focus the laser beam onto disc 2, and to track the recorded spiral pits on disc 2.
As disc 2 rotates, OPU 4 reads information stored on the CD or DVD by scanning the pits and lands on optical disc 2. OPU 4 may contain one or more lasers, optical elements, and associated electronic circuitry, and reads the information stored on disc 2 by detecting the laser beam reflected from disc 2. OPU 4 is usually mounted on a sled which physically positions OPU 4 over disc 2. OPU 4 is capable of reading information from both DVDs and CDs. I/V amplifier 8 converts the photo-diode currents generated by the reflected laser beam into voltages which are supplied to signal amplifier 10 which equalizes the signal representing information read from disc 2.
Servo error detector 12 generates servo error controls signals which are fed back to servo control subsystem 14. The servo error signals include a focus error signal, a tracking error signal, and a track-crossing pulse. Based on the servo error signals received from servo error detector 12, servo control subsystem 14 determines and controls the speed of rotation of disc 2 using servo drivers 16, and also adjusts the height and position of OPU 4 for reading information from disc 2.
Read channel (RC) subsystem 18 extracts bit clock and bit data information for CD and DVD from the output of signal amplifier 10. Read channel subsystem 18 also performs analog-to-digital conversion of the input analog signal. The digital bit stream generated by RC subsystem 18 is provided either to CD-DSP 22 or to DVD-DSP 26 depending on whether playback system 1 is operating in CD or in DVD mode.
CD-DSP 22 demodulates channel bits read from a CD into data bytes and performs error detection and correction on the data bytes. Memory 24 coupled to CD-DSP 22 facilitates de-interleaving operation, and error detection and correction operations. Audio processor 34 coupled with CD-DSP 22 may be used for CD audio playback. The output from CD-DSP 22 may be provided to block decoder 30 or to MPEG decoder 40 via a serial interface. Block decoder 30 performs data block error correction on the CD data and converts the data blocks received from CD-DSP 22 into CD blocks. Memory 32 coupled to block decoder 30 facilitates functions performed by block decoder 30 and also acts as buffer memory for ATAPI interface 36.
DVD-DSP 26 demodulates channel bits read from a DVD into data bytes and performs error detection and correction on the data bytes. DVD-DSP 26 also converts the DVD data into DVD data sector format data. Memory 28 coupled to DVD-DSP 26 facilitates the demodulation, error detection and correction, and data sector formatting operations.
ATAPI interface 36 facilitates the transfer of CD data blocks and DVD sector data to host system CPU 38 using a host system bus. For DVD playback, host system CPU 38 outputs the received data to MPEG decoder 40 using a host system bus, such as ISA/EISA bus. MPEG decoder 40 decompresses and separates the compressed audio and video data. The decompressed video data is output to video playback subsystem 46 for MPEG video playback. The decompressed MPEG audio is output to audio playback subsystem 44 for MPEG-audio or AC3 audio playback.
The ATAPI interface 36 and host CPU 38 are typically required for CD-ROM and DVD and DVD-ROM applications. The CD-ROM/DVD-ROM approach is also used for integrated DVD/CD player applications, but is by no means a cost effective or efficient solution for audio and video playback applications. For a DVD/CD playback system, a 2xc3x97 DVD speed or a 8xc3x97 CD speed is adequate for MPEG playback. Higher speeds which are generally required for CD-ROM and DVD-ROM application are not required for audio and video playback since they do not provide much difference in playback performance.
Microcontroller 48 allows the playback system user to program and control the operations of playback system 1. Microcontroller 48 allows the user to perform various housekeeping functions such as register configuration or setup of playback system 1. Microcontroller 48 facilitates this by providing read and write capabilities for the various registers and memory locations within the various subsystems of playback system 1. Microcontroller 48 also allows the user to monitor the flow of information within the various subsystems of playback system 1. Microcontroller 49 may be programmed to control the functioning of MPEG decoder 40.
As can be seen from FIG. 1, most conventional DVD/CD players use separate subsystems to process information read from CDs and DVDs since the format of the information is different. The various subsystems are generally incorporated into separate chips, each dedicated to processing information of a particular format. The separate subsystems occupy valuable real estate in the playback system and as a whole make the playback system bulky and expensive. Use of separate subsystems for information processing also results in inefficient use of system processing and memory resources and hinders efficient sharing of distributed resources. Further, an increased number of chips also increases the total pin count of playback system I making it bulky and complex. All of the above mentioned factors eventually translate to increased manufacturing costs for the playback system.
Additionally, because of low bit rate associated with CDs (user bit rate is only 1.4112 Mbit/sec for 1xc3x97 CD), most conventional CD-DSP controllers use a serial interface to communicate with external subsystems such as MPEG decoder 40 or block decoder 30. The serial interface is a cost effective solution for low speed CD. Since the internal data flow in CD-DSP controllers uses a 8-bit data path, to facilitate a serial interface to the external subsystems, parallel to serial conversion is required. The external subsystem is then required to perform a serial-to-parallel conversion for further processing.
With the emergence of DVD technology, which uses a higher user bit rate (11.08 Mbit/sec for 1xc3x97 DVD) than that of CD, normally a parallel interface is provided for data transfer. Therefore, in conventional DVD/CD playback systems, the MPEG decoder normally has to support an 8-bit parallel interface for DVD and a serial interface for CD. The 8-bit parallel to serial conversion at CD controller and the serial to parallel conversion at MPEG decoder not only pose an unnecessary overhead in hardware for the playback system, but also requires an 8-times higher transfer rate for the serial interface. Thus, a new transfer protocol which eliminates the serial interface associated with traditional CD-DSP controllers is desired.
Thus, there is a need for an optimized solution for a CD/DVD playback system to reduce system cost. It is desirable that the playback system process audio and video information read from optical disks in an efficient manner. It is desired that the processing subsystems of the playback system be less complex, occupy less real estate (i.e., use less silicon resulting in smaller dies), have a smaller pin count, make efficient use of memory and processing resources, and be cheaper to manufacture than conventional playback systems. It is also desired that be the playback system not restrict the CD-decoder interface to a serial interface.
The present invention relates to a controller architecture optimized for processing audio and video information in playback systems used for reproducing information stored on optical discs of different formats such as CDs and DVDs. According to one embodiment of the present invention, a DVD/CD controller is disclosed which efficiently processes audio and video information read from a CD or DVD for DVD/CD player applications. According to one aspect of the present invention, the DVD/CD controller includes a unique MPEG interface which facilitates transfer of CD data and DVD data from the DVD/CD controller to a MPEG decoder using a parallel interface. The DVD/CD controller also comprises a read channel subsystem for extracting data and clock information from an input signal and for generating digital signals corresponding to the input signal, a CD-DSP subsystem for performing sync detection and demodulation of CD data as defined by the Red Book standard, a DVD-DSP subsystem for performing sync detection and demodulation of DVD data as defined by standards published by the DVD consortium, an error code correction and detection subsystem, and a memory subsystem.
According to another aspect of the present invention, the parallel MPEG interface eliminates the need for an ATAPI interface or a host CPU for transfer of data from the front-end DSPs to the MPEG decoder. The parallel interface simplifies the data transfer from the DVD/CD controller to the MPEG decoder. Due to the simplified parallel MPEG interface, the DVD/CD controller may also be easily integrated into the MPEG decoder.
According to yet another aspect of the present invention, the parallel MPEG interface eliminates parallel-to-serial and serial-to-parallel conversion overhead problems associated with conventional DVD/CD playback systems. The parallel interface also obviates the need to transfer information at higher rates as in conventional DVD/CD playback systems.
According to another aspect of the present invention, the memory subsystem within the DVD/CD controller provides a common memory resource for the subsystems of the DVD/CD controller such as CD-DSP, DVD-DSP, and error code correction and detection subsystem. The memory subsystem thus provides efficient sharing of memory resources among the subsystems and as a result reduces the number of memory chips required for audio and video processing. This reduces the manufacturing costs of the playback system.
According to still another aspect of the present invention the DVD/CD controller includes a servo subsystem which performs servo operations based on servo error control signals received from a servo error detector, sync pattern information received from the CD-DSP and DVD-DSP, and Hall sensor output received from disc motors rotating the disc.
DVD/CD playback systems incorporating the present invention occupy less real estate, have smaller pin counts, are less complex, and are cheaper to manufacture than conventional playback systems.